The best explanation at this point, says WTMJ News Radio in Milwaukee, may be a spring thaw. “There has been a lot of thawing underground,” George Stone, an instructor of Natural Science at Milwaukee Area Technical College told the station. “(The shaking) could be related to ice melting and the release of the stress the ice creates.”

Whatever’s happening, it sure has Wisconsin talking — and some there hoping it continues. “It was kind of cool,” 19-year-old Tyler Zehren tells the Post-Crescent.